The present invention relates to analgesia equipment, and more particularly to an improved carbon dioxide absorption canister for use with a closed circuit or circle analgesia administering apparatus.
The closed circuit or circle technique for administering an anesthetic or an analgesic such as nitrous oxide employs a patient nose mask, having both an inhalation tube or conduit and an exhalation tube coupled to a carbon dioxide absorption canister. An analgesia gas supply machine is also coupled to the inhalation tube. Check valves are normally associated with the inhalation and exhalation tubes to provide a unidirectional, closed fluid flow circuit from the canister through the mask and back to the canister. Oxygen metabolized to carbon dioxide in the patient's system is replaced by gas from the gas supply machine coupled to the inhalation tube along with an analgesic gas. The advantages of the closed circuit or circle administration technique over the open end administration technique are a reduction in the volume of gas flow from the supply machine by one-half to two-thirds of the amount otherwise required, reduction of exposure for the doctor and his assistants to the hazards of continuous inhalation of nitrous oxide or other analgesic gas, and elimination of the nose mask relief valve. Present equipment for administering anesthetics and analgesics using the closed circuit technique is relatively expensive, relatively bulky, and because of its construction, continuous visual monitoring of the operation of the check valves, the pressure relief valve, and the carbon dioxide absorption medium is especially difficult with present equipment.
It is an object of the present invention to provide an improved, relatively inexpensive, reliable, safe, and corrosion-proof absorption canister for use with closed circuit analgesia equipment. Additional objects of the present invention are to provide a carbon dioxide absorption canister of simple construction having a relief valve that can be coupled to an outside exhaust conduit, to provide a canister having a simple, dual function relief and moisture drain valve, to provide a canister having visually monitorable, check valves incorporated into the canister structure, to provide a canister with a means for visually monitoring the effectiveness of the absorption medium within the canister, to provide a canister that will reduce the possibility of dust from the absorption medium entering the inhalation tube, and to provide a canister having check valves that can be easily removed for maintenance and sterilization.